Project Summary/Abstract Transgender women, assigned a male birth sex who identify along the female gender spectrum, experience substantial mental health disparities and high prevalence of incarceration relative to the US general population. Incarcerated transgender women experience widespread structural and interpersonal forms of stigma, including the denial of necessary healthcare. Cross-sectional research suggests that incarceration experiences contribute to the mental health disparities observed among transgender women with incarceration histories, but longitudinal research is lacking. While prisons provide a unique setting within which to clinically intervene to improve the health of disproportionately incarcerated populations, without culturally and clinically knowledgeable providers, transgender inmates are excluded from this benefit. This F31 aims to improve the health of transgender women across two research aims: (1) Examine the psychosocial health trajectories of transgender women according to their incarceration history using data from a prospective cohort study of US transgender women (n=300). Specifically, we will examine the magnitude of the disparity in depressive distress and substance use at 4, 8, and 12 months comparing transgender women with and without incarceration histories, and test for differences in the intercept and slope of the trajectory between these groups over time. Additionally, we will explore the interaction between person-level (incarceration, demographics) and time- variant (stigma, resilience) predictors of depressive distress and substance use for transgender women to determine risk and protective factors in this population. (2) Develop and pilot test an educational intervention to increase prison healthcare providers' ability to care for transgender inmates. Using an implementation science framework, we will adapt an existing transgender competency training for healthcare providers to be inclusive of the prison context; openly field test the intervention with 70 prison healthcare providers in a non-randomized pilot; and evaluate intervention feasibility and acceptability, and changes in providers' knowledge, attitudes, and behavioral intentions to care for transgender patients at baseline, and immediately and 3 months post- intervention. The proposed research addresses an urgent need to equip prison providers with the knowledge and skills to effectively care for transgender inmates. This pilot intervention will set the stage for future refinement and evaluation via a randomized controlled trial with the long-term goal of implementing this needed intervention in correctional institutions across the US. Thus, this research has far-reaching implications for improving the mental health of transgender women during and after incarceration. Through the completion of this 2-year research and training fellowship, the applicant will gain training in advanced statistical methods, intervention development, and scientific communication. The extensive training provided by a multidisciplinary mentoring team will prepare the applicant for a successful career as an academic mentor and independent researcher working to eliminate mental health disparities in gender minority populations.